What type of crystals are found in pseudogout?

Pseudogout, also known as calcium pyrophosphate dihydrate (CPPD) crystal arthritis, is characterized by the presence of positively birefringent rhomboid-shaped crystals. These crystals are formed from calcium pyrophosphate, which can deposit in the joints, leading to inflammation and pain similar to gout, but they are distinct in the type of crystals involved.

When viewed under polarized light microscopy, these positively birefringent rhomboid crystals exhibit a unique appearance compared to other types of crystals found in various arthritic conditions. In contrast, negatively birefringent uric acid crystals, which are associated with gout, are needle-shaped and differ in both composition and optical properties from those seen in pseudogout.

Calcium phosphate crystals exist but typically do not characterize pseudogout, and crystals of sodium urate are specifically associated with gout rather than pseudogout. Therefore, the identification of positively birefringent rhomboid crystals is a definitive characteristic of pseudogout, distinguishing it from other crystalline arthropathies.